Cutting tool

ABSTRACT

The invention relates to a milling tool  1 , in particular a tubular drill, comprising a shaft  2  and a working piece  3 , wherein at least one cutting edge  8  is provided at the face of the working piece  3  and wherein at least on bore  4  is introduced into the face, the axis of which extends axially parallel or in an angle, preferably between 0° and 20°, with respect to the tool&#39;s axis  5.  With this measure, a milling tool and in particular a tubular drill shall be provided, which can perform a rounding off process simpler and faster without the occurrence of the danger of clogging of the edges.

The invention relates to a milling tool and in particular to a so-calledtubular drill, as it is used by jewellers or goldsmiths for producingpieces of jewellery.

Milling tools and tubular drills of that kind are known. They serve toround off the ends of wires with which jewels are held in their frames.For these purposes, milling tools with precision gear cuttings haveproven its worth, as they are shown e.g. in FIG. 8 in a lateral view andin FIG. 9 in a front view. The milling tool 101 shown therein comprisesa shaft 102 and a working piece 103. The working piece 103 is providedwith a plurality of radially extending cutting edges 108, which convergein the center. Due to this circumstance, there result clearly reducedcutting spaces, which do not guarantee a good chip removal. Therefore,the known milling tools or tubular drills, respectively, tend to clogand get loaded.

It is therefore an object of the present invention to provide a millingtool and in particular a tubular drill which is capable of performingthe rounding off simpler and faster without the danger of clogging thecutting edges.

This object is solved by the features of claim 1.

Due to this embodiment, a milling tool or a tubular drill, respectively,is provided with which a secure chip removal is guaranteed, as asufficiently large area for the chip removal can be provided by means ofthe slits. Thus, the processing is made easier and there occurs noclogging of the cutting edges nor a loading thereof, which also resultsin a better cutting performance of the tool.

Preferred embodiments are described in the subclaims.

According to a preferred further development, the bore is disposedeccentrically, such that its axis extends laterally offset with respectto the tool's axis. By way of this embodiment, a cutting angle isgenerated at the resulting cutting edge, which positively influences thecutting performance of the tool.

The chip removal can further be influenced in a positive sense ifaccording to the preferred embodiment, at least one slit is provided,the following edge of which forms the cutting edge. In this way, an edgeis generated which offers at its front side sufficient space for a goodchip removal through the slit and has at its rear side a sufficientclearance angle for a good penetration of the edge into the material tobe processed.

Preferably, the slit extends from the tool's axis to the outercircumferential surface of the working piece and the following sidesurface of the slit extends substantially through the tool's axis. Thus,the chips can be discharged outwardly. This prevents in addition thatthe edges get clogged.

According to a preferred embodiment, at least two bores are provided,the axes of which extend parallel to each other or in an angle,preferably between 0° to 20°, with respect to the tool's axis and whichare arranged offset laterally with respect to the tool's axis by thesame amount or by different amounts, but in different directions, suchthat the contour of the bores viewed from the front forms a circle beingslightly centrically constricted. Especially this embodiment presents aoptimum relation between the number of edges and the available cuttingspace.

In order to guarantee an optimum chip removal also in this embodiment,preferably two slits are provided, which are arranged such thatrespectively one slit—relative to the rotational direction—is positioneddirectly in front of the contraction. Thus, chips generated by therespective edges can be can be discharged directly through the slits,such that a clogging can be prevented particularly effectively.

According to alternative embodiments, it is also possible to providemore than two cutting edges. If this is the case, it is providedaccording to a preferred embodiment, that the number of eccentric borescorresponds to the number of cutting edges or the number of slits,respectively. Therewith, it is secured that the chips produced by eachedge can be directly discharged from the cutting position, without theoccurrence of clogging.

In case of several edges or bores, it is advantageous for reasons ofmanufacturing if the bores, the slits and the cutting edges are arrangedsuch that there results a symmetric assembly.

The chip removal can be further ameliorated if according to a preferredembodiment, each slit has a smooth, in particular arc-shaped groovebottom. Such a shape positively influences the transport of the chips,as a collection of chips and thus a clogging of the slits can beexcluded.

By way of the shape of the bore, the shape generated at the workpiececan be influenced. Therefore, each bore has, according to a preferredembodiment, when viewed from the side, the shape of a semicircle, suchthat a semicircular shaped end at the workpiece is generated.

However, if a different end form is desired, an other shape of the borecan also be provided. For example, each bore, viewed from the side, canhave the shape of a cone, such that a cone-shaped end is generated atthe workpiece.

Concerning the displacement of the bore and concerning the width of theslits, experiments may be made to a broad extent. However, it has provento be especially appropriate if the displacement of each eccentric boreranges from 0 to a maximum of about 0.25 of the diameter of the workingpiece and if the width of the slits ranges from 0 to a maximum of about0.5 of the diameter of the working piece. Thus, the size of the cuttingspaces and the size of the chip discharge can be coordinated optimally.

Further advantages, features and developments of the present inventionresult from the description of preferred embodiments. It the drawings:

FIG. 1 is a side view of the inventive milling tool,

FIG. 2 is a front view of the inventive milling tool of FIG. 1,

FIG. 3 is the view of FIG. 3, which shows the detailed arrangement ofthe bores,

FIG. 4 is a side view of an alternative embodiment of the inventivemilling tool,

FIG. 5 to 7 are front views of further embodiments of the inventivemilling tool,

FIG. 8 is a side view of a milling tool according to the state of theart, and

FIG. 9 is a front view of the milling tool of FIG. 8.

In FIGS. 1 to 3, a first embodiment of the milling tool 1 is shown,which is in particular used as a tubular drill in jewellery processing.The milling tool 1 comprises a shaft 2, at the front end of which aworking piece 3 is provided. In this embodiment, two bores 4 areintroduced into the working piece 3 from its face side. The bores 4 aredisposed axially parallel to each other and with respect to the tool'saxis 5 and offset by an amount d laterally with respect to the tool'saxis 5, such that there results a slightly constricted circle, whenlooking on the contour of the two bores 4 from the face side of themilling tool 1 (cf. FIG. 3). The amount d of the lateral displacement ofthe bore 4 from the tool's axis 5 can have any value and rangespreferably between 0 to a maximum of about 0.25 of the diameter D of theworking piece 3.

The arrangement of the bores 4 is selected such that there results, onthe whole, a symmetric assembly of the working piece 3. In FIG. 2, thisis discernible particularly well from the fact that the centers 7 of thebores 4 are equally spaced from a symmetric axis of the milling tool 1.

Further, two slits 6 are arranged in the working piece 3, the lower edgeof which, positioned at the back in the rotational direction P, forms acutting edge 8. The slits 6 are positioned exactly such thatrespectively one slit 6 follows one of the contractions 10 formed by thecontour of the bores 4. They are therewith positioned directly in frontof the contraction—relative to the rotational direction P of the millingtool 1 (cf. FIG. 2). Consequently, the following side surface of theslit 6 extends substantially through the tool's axis 5.

The width of the slits 6 can have any size and preferably ranges from 0to a maximum of about 0.5 of the diameter D of the working piece 3.

The groove bottom 9 of the slits 6 is formed smoothly, to guarantee atrouble-free chip removal. It can be shaped flat, as shown in FIG. 1, orarc-shaped, as shown in an alternative embodiment in FIG. 4.

The inventive milling tool 1 is preferably provided with two bores 4,two slits 6 and two cutting edges 8. However, it is also possible toprovide three or four cutting edges 8, as shown in FIGS. 5 and 6. Thearrangement of the bores 4, the slits 6 and the cutting edges 8 is madesuch that, on the whole, there results a symmetric assembly of theworking piece 3 (cf. FIGS. 5 and 6).

As an alternative to the embodiments shown in FIGS. 1 to 6, also onesingle cutting edge 8 can be provided (cf. FIG. 7). If only one singlecutting edge 8 is provided, one could possibly do without thedisplacement of the bore 4. In any case, however, the number of bores 4also corresponds to the number of cutting edges 8 or the number of slits6, respectively.

As an alternative, the bores also can be arranged not axially parallel,i.e. in an angle, preferably between 0° and 20° and further preferredbetween 0° and 10°, with respect to the tool's axis, although this isnot illustrated in FIGS. 1 to 9. Nevertheless, substantially the sameadvantageous effects are achieved as described in the embodimentsaccording to FIGS. 1 to 9.

1. A milling tool, in particular a tubular drill comprising a shaft (2)and a working piece (3), wherein at least one cutting edge (8) is formedin the area of the face of the working piece (3) and wherein at leastone bore (5) is introduced into the face, the axis of which extendsaxially parallel or in an angle, preferably between 0° and 20°, withrespect to the tool's axis (5), and wherein the bore (4) is arrangedeccentrically such that its axis extends laterally offset with respectto the tool's axis (5), characterized in that at least one slit (6) isprovided at the face side, the following edge of which forms the cuttingedge (8) and which extends from the tool's axis (5) to the outercircumferential surface of the working piece (3), wherein the followingside surface of the slit (6) substantially extends through the tool'saxis (5).
 2. The milling tool as claimed in claim 1, characterized inthat at least two bores (4) are provided, the axes of which extendaxially parallel to each other or in an angle, preferably between 0° to20°, with respect to the tool's axis (5) and which are arranged offsetlaterally with respect to the tool's axis (5) by the same amount or bydifferent amounts, but in different directions, such that the contour ofthe bores (4) viewed from the face side forms a circle being slightlycentrically constricted.
 3. The milling tool as claimed in claim 1,wherein two slits (6) are provided which are arranged such thatrespectively one slit (6)—relative to the rotational direction (P)—isdisposed directly in front of a contraction (10).
 4. The milling tool asclaimed in claim 1, wherein a plurality of cutting edges (8) is providedand wherein the number of eccentric bores (4) corresponds to the numberof cutting edges (8) or the number of slits (6), respectively.
 5. Themilling tool as claimed in claim 1, wherein the bores (4), the slits (6)and the cutting edges (8) are arranged such that a symmetric assemblyresults.
 6. The milling tool as claimed in claim 1, wherein each slit(6) includes a smooth, in particular arc-shaped groove bottom (9). 7.The milling tool as claimed in claim 1, wherein each bore (4)—viewedfrom the side—has the shape of a semicircle.
 8. The milling tool asclaimed in claim 1, wherein each bore (4)—viewed from the side—has theshape of a cone.
 9. The milling tool as claimed in claim 1, wherein thedisplacement (d) of each bore (4) ranges from 0 to a maximum of about0,25 of the diameter (D) of the working piece (3).
 10. The milling toolas claimed in claim 1, wherein the width (b) of the slits (6) rangesfrom 0 to a maximum of about 0,5 of the diameter (D) of the workingpiece (3).
 11. The milling tool as claimed in claim 2, wherein two slits(6) are provided which are arranged such that respectively one slit(6)—relative to the rotational direction (P)—is disposed directly infront of a contraction (10).
 12. The milling tool as claimed in claim 2,wherein a plurality of cutting edges (8) is provided and wherein thenumber of eccentric bores (4) corresponds to the number of cutting edges(8) or the number of slits (6), respectively.
 13. The milling tool asclaimed in claim 2, wherein the bores (4), the slits (6) and the cuttingedges (8) are arranged such that a symmetric assembly results.
 14. Themilling tool as claimed in claim 2, wherein each slit (6) includes asmooth, in particular arc-shaped groove bottom (9).
 15. The milling toolas claimed in claim 2, wherein each bore (4)—viewed from the side—hasthe shape of a semicircle.
 16. The milling tool as claimed in claim 2,wherein each bore (4)—viewed from the side—has the shape of a cone. 17.The milling tool as claimed in claim 2, wherein the displacement (d) ofeach bore (4) ranges from 0 to a maximum of about 0,25 of the diameter(D) of the working piece (3).
 18. The milling tool as claimed in claim2, wherein the width (b) of the slits (6) ranges from 0 to a maximum ofabout 0,5 of the diameter (D) of the working piece (3).
 19. The millingtool as claimed in claim 3, wherein a plurality of cutting edges (8) isprovided and wherein the number of eccentric bores (4) corresponds tothe number of cutting edges (8) or the number of slits (6),respectively.
 20. The milling tool as claimed in claim 3, wherein thebores (4), the slits (6) and the cutting edges (8) are arranged suchthat a symmetric assembly results.